1. Field of the Invention
The present invention relates to a method and apparatus for filling liquid into a desired position. In particular, it relates to a liquid filling method to fill expensive reagents, scarce specimens, or the like, a liquid filling apparatus, and furthermore a discharge apparatus incorporating the filling apparatus.
2. Description of Related Art
There has been remarkable progress in methods of analyzing gene structures in recent years, and large numbers of gene structures have been identified, including the human gene and others. For such analysis of gene structures, a method is used in which thousands to tens of thousands or more different DNA fragments are placed and aligned on a substrate such as a microscope slide glass or the like in droplets, forming test objects, and they are observed by microscope or the like.
However, in the case where thousands or more objects are produced, such as when producing test objects, it is very inefficient to carry out this operation totally manually. Therefore, automation is required.
A method of automation that can be used is a filling apparatus that discharges liquid such as a reagent or the like, and fills it into test objects. An example of a filling apparatus for discharging liquid is a droplet discharge apparatus, called an inkjet apparatus, used in printers and the like as described in Japanese Unexamined Patent Application, First Publication No. 2001-324505.
Typically, such a droplet discharge apparatus is provided with a liquid cavity tank behind a discharge head, and supplies liquid from the liquid cavity tank to the discharge head, and discharges droplets (liquid) from the nozzles of the discharge head.
However, for producing test objects or the like using DNA fragments as mentioned previously, specimens to be used such as DNA or the like are scarce, and many reagents to be used are expensive. Therefore, it is difficult to collect a large quantity of liquid as a reagent in the liquid cavity tank, and supply it to the discharge head to discharge droplets (liquid) from the nozzles. This is because in the case where liquid is discharged from the discharge head, evidently the liquid fills the discharge head, and in order to discharge it accurately, it is necessary to prevent air (air bubbles) from entering and remaining in the discharge path, or to remove residual air bubbles.
However, as mentioned above, in the case where a liquid cavity tank is provided, liquid must fill the path from the liquid cavity tank to the discharge head, and also a test discharge of the liquid must be performed in order to remove air (air bubbles) mixed therein. Consequently, a large amount of liquid (reagent) is required, and a lot is wasted, which is a cost disadvantage, so basically this method cannot be used for scarce liquids.
The present invention takes the above situations into consideration, with an object of providing a liquid filling method that can fill expensive reagents, scarce specimens, or the like, easily and reliably, a liquid filling apparatus, and a discharge apparatus incorporating the filling apparatus.